A Bidirectional Quasi-Endfire Patch Antenna with Low Elevation Angle

A bidirectional quasi-endfire patch antenna with a low elevation angle has promising applications for wireless communication systems that are vehicle-based, airborne, and shipborne. In this paper, the shortened patch resonators and open patch resonator are integrated to form a bidirectional quasi-endfire patch antenna with low elevation angle. The open patch resonator operates with a TM₂₀ mode to realize bidirectional radiation. The two shortened patch resonators operate with a TM₀₁ mode coupled with a TM₂₀ mode to control the phase difference between them at a suitable angle, so that the shortened patch resonators act as directors to tilt the dual beams toward the endfire direction and achieve low elevation angle. Compared with reported patch antennas with dual beams, the proposed antenna has the lowest elevation angle and a compact structure. For demonstration purposes, an antenna prototype operating at 3.5 GHz is fabricated and measured, exhibiting a low elevation angle of ±28°, a -10 dB impedance matching bandwidth from 3.44 GHz to 3.61 GHz, and a size of 1.36 λ₀ × 0.57 λ₀ with a profile of 0.036 λ₀. A prototype with two pair of shortened patch directors further reduces the elevation angle to ±19° with the size of 2.3 λ₀ × 0.57 λ₀.